1. Field of the Invention
This invention relates to the field of high-temperature superconductors. More specifically, the invention comprises a method for making a reinforced composite Bi2212 superconductor using an embedded internal oxygen source.
2. Description of the Related Art
Composite conductors for use in electromagnets are well known in the art. The term “composite” is intended to encompass a structure containing two or more different materials formed into a unified assembly. It is known to use bismuth compounds to create a high-temperature superconducting cables. Bi2212 wire has been used for this purpose.
The Bi2212 wire is combined with other materials—such as a copper or silver matrix—and progressively passed through forming processes to bond the materials together longitudinally. One example is the use of drawing dies to compress a bundle of round conductors and cause the constituents to plastically deform around each other and thereby create a unified whole.
Those skilled in the art will know that heat treatment processes are typically employed when forming a Bi-2212 composite conductor. Existing Bi2212 wires require an external oxygen supply during the heat treatment process. These processes are typically performed in a 100% oxygen atmosphere or at least an atmosphere containing a significant amount of oxygen. The oxygen is chemically active at the temperatures required for the heat treatment and will often react with other materials to produce unwanted results. This fact limits the component design choices available, since the undesired oxidation of some components must be considered. The present invention seeks to reduce this problem by providing an internal oxygen source within the composite conductor in combination with an external barrier on the outer diameter of the composite that is impervious to oxygen to prevent migration of the oxygen out of the composite.